The demonstration of protection by SIV and HIV vaccines in primates has led to cautious optimism for a protective vaccine against AIDS. To translate the findings from primates to an effective HIV vaccine in people, it is essential to understand what immune responses provide protection and against which antigen(s) immunity is directed. However, assessment of immune responses in primates is difficult and requires expertise generally not available at primate centers, where the best animal resources are located. For example, MHC (major histocompatibility complex) typing is essential for evaluation of cytotoxic T lymphocyte (CTL) responses, but reagents and expertise have been limited. Standard protocols for assessment of cell-mediated immune responses are still being developed. Analysis of virus neutralization with stocks used for animal challenge is problematic and assays vary between laboratories. Furthermore, these assessments are time-consuming and labor-intensive. Focusing resources in a centralized site is expected to advance the field rapidly, providing the necessary data to compare the immune responses that different vaccines can produce and to correlate them with protection. Three NIAID contract-supported SIV Vaccine Evaluation Units (SIV VEUs) are currently involved in the SIV vaccine evaluations: the Tulane University Delta Regional Primate Research Center, the Washington Regional Primate Research Center, and the TSI Mason Research Institute. In addition, access to a limited number of chimpanzees has been funded through an Interagency Agreement with the National Cancer Institute (NCI). The chimpanzees are housed at the NCI facilities at the New Mexico State University Primate Center. These agreements provide only limited immunological evaluation. This Primate Core Immunology Laboratory contract will adapt, standardize, and perform assays for cellular and humoral immune responses induced in primates by immunization with prototype AIDS vaccines tested at the SIV VEUs, the Chimpanzee Unit, and other Preclinical AIDS Vaccine Trials, such as those being conducted by the NCI or the United States Army, if required.